How many fish in a 125 gallon tank?
A 6 ft tank for large fish, big schools and active swimmers.
A 125 gallon tank (473 L) can hold roughly 208 small fish like neon tetras on their own, or a smaller mixed community. Big fish count for much more than small ones, so plan by adult size and waste, not inches per gallon.
125 gallon stocking ideas
Each plan is checked by our calculator for space, water and compatibility. Add fish gradually to a cycled tank.
Discus tank
- 6 × Discus
- 20 × Cardinal tetras
- 8 × Sterbai corydoras
Discus need very warm, soft, pristine water and frequent water changes.
Fast-swimmer tank
- 10 × Giant danios
- 8 × Denison barbs
Active schooling fish that use the full 6 ft length. Keep the lid on, giant danios jump.
Equipment for a 125 gallon tank
Sized for a 125 gallon tank (72 × 18 × 21 in) with tropical community fish. Your fish may need extras: the stocking calculator builds a list for your exact plan.
- 125 gallon aquarium (tank or kit) (opens Amazon in a new tab)Bigger tanks are more stable and easier for beginners. How to choose
- Aquarium stand for 125 gallons (opens Amazon in a new tab)The water alone weighs about 1043 lb (473 kg), before glass, gravel and rock. How to choose
- 2 adjustable heaters, 250 W each (opens Amazon in a new tab)Holds about 78 °F (25.5 °C) in a room at 65 °F (18 °C). Two heaters keep the tank warm if one fails. How to choose
- Aquarium thermometer (opens Amazon in a new tab)Check it daily: heaters can fail stuck on or off. How to choose
- Canister filter rated 500–750 GPH (opens Amazon in a new tab)Community tank: 4–6 times the tank volume per hour. How to choose
- About 150 lb of aquarium gravel (opens Amazon in a new tab)Enough for a layer about 2 in (5 cm) deep. Smooth gravel suits most community fish. How to choose
- Water conditioner (dechlorinator) (opens Amazon in a new tab)Removes chlorine and chloramine from tap water. Seachem Prime is a popular, concentrated choice. How to choose
- Liquid test kit (ammonia, nitrite, nitrate, pH) (opens Amazon in a new tab)Liquid kits are more accurate than strips. The API Freshwater Master Test Kit is the common choice. How to choose
- Gravel vacuum (siphon) (opens Amazon in a new tab)Cleans the gravel and does the water change in one go. How to choose
- LED aquarium light, about 72 in long (opens Amazon in a new tab)Match the light to the tank length. Basic LEDs grow easy plants. How to choose
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Fish that suit a 125 gallon tank
The number is the most you could keep of that species alone, by bioload. Mix species and you'll need fewer of each.
| Species | Adult size | Keep |
|---|---|---|
| Angelfish | 15 cm (5.9 in) | 1 male |
| Betta fish | 6.5 cm (2.6 in) | 1 male |
| Bristlenose pleco | 12 cm (4.7 in) | 1 male |
| Bronze corydoras | 7 cm (2.8 in) | 6–73 |
| Common goldfish | 30 cm (11.8 in) | 1–4 |
| Dwarf gourami | 7.5 cm (3 in) | 1 male |
| Fancy goldfish | 15 cm (5.9 in) | 1–11 |
| Guppy | 5 cm (2 in) | 3–121 |
| Neon tetra | 3.5 cm (1.4 in) | 8–208 |
| Oscar | 30 cm (11.8 in) | 1 or a pair |
| Panda corydoras | 4.5 cm (1.8 in) | 6–142 |
| Tiger barb | 7 cm (2.8 in) | 8–61 |
| Zebra danio | 5 cm (2 in) | 6–121 |
| Black skirt tetra | 6 cm (2.4 in) | 8–84 |
| Blood parrot cichlid | 20 cm (7.9 in) | 1 male |
| Boesemani rainbowfish | 10 cm (3.9 in) | 6–35 |
| Cardinal tetra | 4 cm (1.6 in) | 8–170 |
| Celestial pearl danio | 2.5 cm (1 in) | 8–344 |
| Cherry barb | 5 cm (2 in) | 6–121 |
| Chili rasbora | 2 cm (0.8 in) | 10–481 |
| Chinese algae eater | 25 cm (9.8 in) | 1 |
| Convict cichlid | 12 cm (4.7 in) | 1 or a pair |
| Denison barb | 13 cm (5.1 in) | 6–29 |
| Discus | 15 cm (5.9 in) | 5–16 |
| Dojo loach | 15 cm (5.9 in) | 3–29 |
| Dwarf neon rainbowfish | 6 cm (2.4 in) | 6–92 |
| Electric blue acara | 15 cm (5.9 in) | 1 or a pair |
| Electric yellow cichlid | 10 cm (3.9 in) | 4–28 (few males) |
| Ember tetra | 2 cm (0.8 in) | 8–481 |
| Firemouth cichlid | 13 cm (5.1 in) | 1 or a pair |
| German blue ram | 6 cm (2.4 in) | 1 or a pair |
| Glowlight tetra | 4 cm (1.6 in) | 6–170 |
| Harlequin rasbora | 4.5 cm (1.8 in) | 8–142 |
| Hillstream loach | 6.5 cm (2.6 in) | 3–82 |
| Honey gourami | 5 cm (2 in) | 1 male |
| Jack Dempsey | 20 cm (7.9 in) | 1 or a pair |
| Julii corydoras | 5.5 cm (2.2 in) | 6–105 |
| Kribensis | 10 cm (3.9 in) | 1 or a pair |
| Kuhli loach | 9 cm (3.5 in) | 6–84 |
| Molly | 10 cm (3.9 in) | 3–35 (few males) |
| Otocinclus | 4 cm (1.6 in) | 6–170 |
| Pea puffer | 2.5 cm (1 in) | 1 male + 2 or more females |
| Peacock cichlid | 13 cm (5.1 in) | 1 male + 2 or more females |
| Pearl gourami | 11.5 cm (4.5 in) | 1 male + 2 or more females |
| Peppered corydoras | 6.5 cm (2.6 in) | 6–82 |
| Pictus catfish | 13 cm (5.1 in) | 3–24 |
| Platy | 6 cm (2.4 in) | 3–92 |
| Pygmy corydoras | 2.5 cm (1 in) | 10–344 |
| Rainbow shark | 15 cm (5.9 in) | 1 |
| Red zebra cichlid | 11 cm (4.3 in) | 4–24 (few males) |
| Red-tail shark | 12 cm (4.7 in) | 1 |
| Rosy barb | 9 cm (3.5 in) | 6–42 |
| Rummy-nose tetra | 5 cm (2 in) | 10–121 |
| Senegal bichir | 30 cm (11.8 in) | 1–8 |
| Siamese algae eater | 15 cm (5.9 in) | 1–23 |
| Silver dollar | 15 cm (5.9 in) | 5–19 |
| Sterbai corydoras | 6.5 cm (2.6 in) | 6–82 |
| Three spot gourami | 12 cm (4.7 in) | 1 male |
| White cloud mountain minnow | 4 cm (1.6 in) | 6–170 |
| X-ray tetra | 4.5 cm (1.8 in) | 6–142 |
| Yoyo loach | 13 cm (5.1 in) | 5–26 |
| African butterfly fish | 11 cm (4.3 in) | 1 male |
| Agassiz's dwarf cichlid | 7 cm (2.8 in) | 1 male + 2 or more females |
| Black ghost knifefish | 45 cm (17.7 in) | 1 |
| Black neon tetra | 4 cm (1.6 in) | 8–170 |
| Black phantom tetra | 4 cm (1.6 in) | 6–170 |
| Bleeding heart tetra | 6.5 cm (2.6 in) | 8–74 |
| Bloodfin tetra | 5 cm (2 in) | 6–121 |
| Bolivian ram | 8 cm (3.1 in) | 1 or a pair |
| Buenos Aires tetra | 7 cm (2.8 in) | 8–61 |
| Bumblebee catfish | 7.5 cm (3 in) | 1–55 |
| Clown killifish | 3.5 cm (1.4 in) | 6–208 |
| Clown pleco | 9 cm (3.5 in) | 1 male |
| Cockatoo cichlid | 7.5 cm (3 in) | 1 male + 2 or more females |
| Congo tetra | 8 cm (3.1 in) | 6–54 |
| Demasoni cichlid | 8 cm (3.1 in) | 12–40 (few males) |
| Diamond tetra | 6 cm (2.4 in) | 6–84 |
| Dwarf chain loach | 6 cm (2.4 in) | 6–92 |
| Emerald green corydoras | 8 cm (3.1 in) | 6–60 |
| Emperor tetra | 5 cm (2 in) | 6–121 |
| Endler's livebearer | 3 cm (1.2 in) | 3–262 |
| Forktail blue-eye | 5 cm (2 in) | 8–121 |
| Gardneri killifish | 6 cm (2.4 in) | 1 male + 2 or more females |
| Giant danio | 10 cm (3.9 in) | 6–43 |
| Glass catfish | 7 cm (2.8 in) | 6–73 |
| Gold barb | 7 cm (2.8 in) | 6–61 |
| Golden wonder killifish | 9 cm (3.5 in) | 1 male + 2 or more females |
| Green terror | 20 cm (7.9 in) | 1 or a pair |
| Head and tail light tetra | 4.5 cm (1.8 in) | 6–142 |
| Jewel cichlid | 10 cm (3.9 in) | 1 or a pair |
| Kissing gourami | 20 cm (7.9 in) | 1 |
| Kubotai rasbora | 2 cm (0.8 in) | 10–481 |
| Lambchop rasbora | 3.5 cm (1.4 in) | 8–208 |
| Lemon tetra | 4.5 cm (1.8 in) | 8–142 |
| Marbled hatchetfish | 3.5 cm (1.4 in) | 8–208 |
| Odessa barb | 6 cm (2.4 in) | 6–84 |
| Panda garra | 8.5 cm (3.3 in) | 3–54 |
| Paradise fish | 8 cm (3.1 in) | 1 male |
| Peacock gudgeon | 6 cm (2.4 in) | 2–92 (few males) |
| Penguin tetra | 5 cm (2 in) | 6–121 |
| Red rainbowfish | 12 cm (4.7 in) | 6–27 |
| Ropefish | 35 cm (13.8 in) | 1–9 |
| Rosy loach | 2.5 cm (1 in) | 8–344 |
| Rosy tetra | 4 cm (1.6 in) | 6–170 |
| Rubber lip pleco | 14 cm (5.5 in) | 1 |
| Scarlet badis | 2 cm (0.8 in) | 1 male + 2 or more females |
| Scissortail rasbora | 12 cm (4.7 in) | 6–32 |
| Serpae tetra | 4.5 cm (1.8 in) | 10–142 |
| Severum | 20 cm (7.9 in) | 1 or a pair |
| Shell dweller cichlid | 4 cm (1.6 in) | 2–170 (few males) |
| Sparkling gourami | 3.8 cm (1.5 in) | 2–153 |
| Swordtail | 12 cm (4.7 in) | 4–32 (few males) |
| Threadfin rainbowfish | 4 cm (1.6 in) | 6–170 |
| Turquoise rainbowfish | 11 cm (4.3 in) | 6–31 |
| Upside-down catfish | 9.5 cm (3.7 in) | 4–38 |
| Zebra loach | 9 cm (3.5 in) | 5–50 |
| Zebra pleco | 8 cm (3.1 in) | 1 male |
| Black ruby barb | 6 cm (2.4 in) | 6–84 |
| Checkerboard barb | 5 cm (2 in) | 6–121 |
| Dwarf rasbora | 2.5 cm (1 in) | 10–344 |
| Flame tetra | 3 cm (1.2 in) | 8–262 |
| Glowlight danio | 3.5 cm (1.4 in) | 6–208 |
| Green neon tetra | 2.5 cm (1 in) | 10–344 |
| Keyhole cichlid | 10 cm (3.9 in) | 2–33 |
| Least killifish | 2.5 cm (1 in) | 6–344 |
| Moonlight gourami | 14 cm (5.5 in) | 1 male |
| Pearl danio | 6 cm (2.4 in) | 6–92 |
| Silvertip tetra | 4.5 cm (1.8 in) | 8–142 |
| Thick-lipped gourami | 9 cm (3.5 in) | 1 male |
| Variatus platy | 6 cm (2.4 in) | 3–92 |
Shrimp, snails and other invertebrates
Cherry shrimp, Nerite snail, African dwarf frog, Amano shrimp, Assassin snail, Ghost shrimp, Malaysian trumpet snail, Mystery snail, Ramshorn snail, Bamboo shrimp, Crystal red shrimp, Dwarf orange crayfish, Rabbit snail, Thai micro crab, Vampire shrimp.
Fish that need a bigger tank
- Common pleco: at least 150 gallons (568 L)
- Bala shark: at least 230 gallons (871 L)
- Clown loach: at least 180 gallons (681 L)
Frequently asked questions
How many fish can go in a 125 gallon tank?
A 125 gallon tank (473 L) can hold roughly 208 small fish like neon tetras on their own, or a smaller mixed community. Big fish count for much more than small ones, so plan by adult size and waste, not inches per gallon.
What are the best fish for a 125 gallon tank?
Good choices include angelfish, betta fish, bristlenose pleco, bronze corydoras, common goldfish and dwarf gourami. Pick one centerpiece or one school plus a few bottom dwellers, then check the mix in our stocking calculator.
How big is a 125 gallon tank?
A standard 125 gallon tank is about 72 × 18 × 21 inches (183 × 46 × 53 cm). Full of water it weighs at least 1043 lb (473 kg) before glass, gravel and decor.
What fish should not go in a 125 gallon tank?
Common plecos, bala sharks and clown loaches need more room. For example, common plecos need at least 150 gallons (568 L).
What size heater do I need for a 125 gallon tank?
About 2 heaters of 250 W keeps a 125 gallon tank at 78 °F (25.5 °C) in a room at 65 °F (18 °C). Use a bigger heater for a colder room, or check yours with our heater size calculator.
What size filter do I need for a 125 gallon tank?
Choose a filter rated about 500–750 gallons per hour (GPH), which is 4–6 times the tank volume for a typical community tank. Messy fish like goldfish need more; bettas need gentle flow.